Vital signs monitor used for conditioning a patient&#39;s response

ABSTRACT

The invention provides a method for monitoring a patient, comprising the following steps: 1) outfitting the patient with a ambulatory blood pressure monitor that features an optical system for measuring blood pressure without using a cuff, and a wireless system configured to send and receive information sent from an Internet-based system through a wireless network; 2) sending from the Internet-based system to the ambulatory blood pressure monitor a signal that indicates a blood pressure level; 3) comparing a blood pressure value measured with the ambulatory blood pressure monitor to the blood pressure level; and 4) generating a signal in response to the comparing step.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/752,198, filed on Jan. 6, 2004.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates to medical devices for monitoring vitalsigns such as heart rate, pulse oximetry, and blood pressure, and usingthis information to condition a patient's response.

DESCRIPTION OF THE RELATED ART

Pulse oximeters are medical devices featuring an optical module,typically worn on a patient's finger or ear lobe, and a processingmodule that analyzes data generated by the optical module. The opticalmodule typically includes first and second light sources (e.g.,light-emitting diodes, or LEDs) that transmit optical radiation at,respectively, red (λ˜630-670 nm) and infrared (λ˜800-1200 nm)wavelengths. The optical module also features a photodetector thatdetects radiation transmitted or reflected by an underlying artery.Typically the red and infrared LEDs sequentially emit radiation that ispartially absorbed by blood flowing in the artery. The photodetector issynchronized with the LEDs to detect transmitted or reflected radiation.In response, the photodetector generates a separate radiation-inducedsignal for each wavelength. The signal, called a plethysmograph, variesin a time-dependent manner as each heartbeat varies the volume ofarterial blood and hence the amount of transmitted or reflectedradiation. A microprocessor in the pulse oximeter processes the relativeabsorption of red and infrared radiation to determine the oxygensaturation in the patient's blood. A number between 94%-100% isconsidered normal, while a value below 85% typically indicates thepatient requires hospitalization. In addition, the microprocessoranalyzes time-dependent features in the plethysmograph to determine thepatient's heart rate.

Pulse oximeters work best when the appendage they attach to (e.g., afinger) is at rest. If the finger is moving, for example, the lightsource and photodetector within the optical module typically moverelative to the hand. This generates ‘noise’ in the plethysmograph,which in turn can lead to motion-related artifacts in data describingpulse oximetry and heart rate. Ultimately this reduces the accuracy ofthe measurement. Various methods have been disclosed for using pulseoximeters to obtain arterial blood pressure values for a patient. Onesuch method is disclosed in U.S. Pat. No. 5,140,990 to Jones et al., fora ‘Method Of Measuring Blood Pressure With a Photoplethysmograph’. The'990 patent discloses using a pulse oximeter with a calibrated auxiliaryblood pressure monitor to generate a constant that is specific to apatient's blood pressure. Another method for using a pulse oximeter tomeasure blood pressure is disclosed in U.S. Pat. No. 6,616,613 toGoodman for a ‘Physiological Signal Monitoring System’. The '613 patentdiscloses processing a pulse oximetry signal in combination withinformation from a calibrating device to determine a patient's bloodpressure.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a cuffless blood-pressure monitor thatfeatures a behavior modification system. The blood pressure monitor istypically worn on a patient's head and makes a transdermal, opticalmeasurement of blood pressure, which it then sends to a processingcomponent (e.g., a PDA). The processing component preferably features anembedded, short-range wireless transceiver and a software platform thatdisplays, analyzes, and then transmits the information through awireless network to an Internet-based system. This system generates anaudio or visual alarm when the patient's blood pressure trends high, andthus the patient may modify their behavior through conditioned response.In addition, a medical professional can continuously monitor a patient'sblood pressure during their day-to-day activities. Monitoring patientsin this manner minimizes erroneous measurements due to ‘white coatsyndrome’, increases the accuracy of a blood-pressure measurement andadditionally allows patients to modify behavior to lower blood pressurewhile wearing the device.

The invention has many advantages. In particular, one aspect of theinvention provides a system that continuously monitors a patient's bloodpressure using a cuffless blood pressure monitor and an off-the-shelfmobile communication device. Information describing the blood pressurecan be viewed using an Internet-based website, using a personalcomputer, or simply by viewing a display on the mobile device.Blood-pressure information measured continuously throughout the dayprovides a relatively comprehensive data set compared to that measuredduring isolated medical appointments. This approach identifies trends ina patient's blood pressure, such as a gradual increase or decrease,which allows for the patient to view and conditionally respond to highblood pressure through behavior modification such as breathingexercises. The monitor can also characterize the patient's heart rateand blood oxygen saturation using the same optical system for theblood-pressure measurement. This information can be wirelesslytransmitted along with blood-pressure information and used to furtherdiagnose the patient's cardiac condition. The monitor is small, easilyworn by the patient during periods of exercise or day-to-day activities,and makes a non-invasive blood-pressure measurement in a matter ofseconds. The resulting information has many uses for patients, medicalprofessionals, hospitals, insurance companies, pharmaceutical agenciesconducting clinical trials, and organizations for home-healthmonitoring.

In one aspect, the invention provides a system for measuring bloodpressure from a patient that features: 1) an optical module configuredto be worn on (or in) the patient's head that includes at least oneoptical source and a photodetector; 2) a calibration source configuredto make a blood pressure measurement; and, 3) a processing moduleconfigured to: i) receive a first signal from the optical module; ii)receive a second signal from the calibration source; iii) process thefirst and second signals to generate a calibration table; and iv)receive a third signal from the optical module and compare it to thecalibration table to determine the patient's blood pressure.

The preferred invention includes a response alert system designed toalert the patient when escalated vital signs reach dangerously harmfullevels. The alert system alerts the patient when blood pressure levelsreach dangerous levels caused by stress and anxiety. Each patient'sblood pressure level parameters are set during the time of calibrationby a physician.

In embodiments, the blood pressure monitor features a head-worn clipthat includes the optical module (e.g., a photodetector and first andsecond LEDs that emit, respectively, red radiation and infraredradiation). The optical calibration source is typically a cuff-basedblood pressure module that includes a cuff and a pump worn around thepatient's arm. In other embodiments, the optical module includes ashort-range wireless transmitter configured to send signals to theprocessing module, which in turn may include a matched short-rangewireless receiver.

The short-range wireless transceiver preferably operates on a wirelessprotocol such as Bluetooth™, 802.15.4 or 802.11. The long-range wirelesstransmitter preferably transmits information over a terrestrial,satellite, or 802.11-based wireless network. Suitable networks includethose operating at least one of the following protocols: CDMA, GSM,GPRS, Mobitex, DataTac, iDEN, and analogs and derivatives thereof.

In addition, the cuffless blood pressure-measuring device of theinvention combines all the benefits of conventional cuff-basedblood-pressure measuring devices without any of the obvious drawbacks(e.g., restrictive, uncomfortable cuffs). Its measurement is basicallyunobtrusive to the patient, and thus alleviates conditions, such as apoorly fitting cuff, that can erroneously affect a blood-pressuremeasurement. The device is small and makes a non-invasive blood-pressuremeasurement in a matter of seconds. An on-board or remote processor cananalyze the time-dependent measurements to generate statistics on apatient's blood pressure (e.g., average pressures, standard deviation,beat-to-beat pressure variations) that are not available withconventional devices that only measure systolic and diastolic bloodpressure.

These and other advantages of the invention will be apparent from thefollowing detailed description and from the claims.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a semi-schematic diagram of a method for developing aconditioned response that utilizes the cuffless ambulatoryblood-pressure monitor of the invention;

FIGS. 2A and 2B are semi-schematic views of the cuffless ambulatoryblood-pressure monitor of FIG. 1 featuring a head-band with an opticalsystem and a wireless hub connected, respectively, by a cable andshort-range wireless connection;

FIG. 3 is a semi-schematic view of a calibration process used with theambulatory blood-pressure monitor of FIGS. 2A and 2B;

FIG. 4 is a schematic view of an Internet-based system that operateswith the ambulatory blood-pressure monitor of FIGS. 2A and 2B;

FIG. 5A is a schematic top view of an adhesive patch sensor thatmeasures blood pressure according to the invention;

FIG. 5B is a schematic, cross-sectional view of the patch sensor of FIG.1A; and

FIG. 6 is a graph of time-dependent optical and electrical waveformsgenerated by the patch sensor of FIG. 5A.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a semi-schematic diagram illustrating a conditionedresponse alert system 8 that features an ambulatory blood pressuremonitor (ABPM) according to the invention. In preferred embodiments, aphysician prescribes to a patient an ABPM that identifies harmfully highblood pressure levels using the conditioned response alert system 8.While outfitting the patient, the physician sets vital signs parameterlimits, e.g. blood pressure limits, into the ABPM that indicate when anaudio alarm will sound (step 1). Patients typically wear the ABPM for anextended period of time, during which they are typically exposed tostressful situations that may cause their blood pressure to rise (step2). As blood pressure levels elevate into dangerously high levels, theABPM emits an audio response and/or a visual alert that indicates highblood pressure levels (step 3). The patient responds to the alert (step4) by, e.g., using breathing and other relaxation techniques to lowertheir blood pressure (step 5), or by activating a ‘snooze’ feature onthe monitor to delay the alert (step 6). Over time the patient developsa conditioned response to the alert and becomes aware that theirblood-pressure levels are dangerously high. Ultimately this lowers thepatient's blood pressure, thereby reducing the chance that a seriousmedical condition, e.g. heart attack or stroke, occurs.

As shown in FIGS. 2A and 2B, the ABPM 20 typically features an opticalhead-mounted component 105 that attaches to a patient's head 70, and aprocessing component 19 that preferably attaches to the patient's belt.In a preferred embodiment, a cable 118 provides an electrical connection81 between the head-mounted component 105 and the processing component19. During operation, the head-mounted component 105 measures opticaland electrical ‘waveforms’, described in more detail below, that theprocessing component 19 processes to determine real-time beat-to-beatdiastolic and systolic blood pressure, heart rate, and pulse oximetry.The processing component also includes an internal wireless system thatrelays this information to an Internet-based system through an antenna86.

Methods for processing the optical and electrical waveform to determineblood pressure are described in the following co-pending patentapplications, the entire contents of which are incorporated byreference: 1) CUFFLESS BLOOD-PRESSURE MONITOR AND ACCOMPANYING WIRELESS,INTERNET-BASED SYSTEM (U.S. Ser. No. 10/709,015; filed Apr. 7, 2004); 2)CUFFLESS SYSTEM FOR MEASURING BLOOD PRESSURE (U.S. Ser. No. 10/709,014;filed Apr. 7, 2004); 3) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYINGWEB SERVICES INTERFACE (U.S. Ser. No. 10/810,237; filed Mar. 26, 2004);4) VITAL-SIGN MONITOR FOR ATHLETIC APPLICATIONS (U.S. Ser. No.; filedSep. 13, 2004); 5) CUFFLESS BLOOD PRESSURE MONITOR AND ACCOMPANYINGWIRELESS MOBILE DEVICE (U.S. Ser. No. 10/967,511; filed Oct. 18, 2004);6) BLOOD PRESSURE MONITORING DEVICE FEATURING A CALIBRATION-BASEDANALYSIS (U.S. Ser. No. 10/967,610; filed Oct. 18, 2004); 7) PERSONALCOMPUTER-BASED VITAL SIGN MONITOR (U.S. Ser. No. 10/906,342; filed Feb.15, 2005); and 8) PATCH SENSOR FOR MEASURING BLOOD PRESSURE WITHOUT ACUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005).

FIG. 2B shows an alternate embodiment of the invention wherein anoptical patch sensor 106 sends vital-sign information to a processingcomponent 18 using a short-range wireless link 24. In this embodimentthe optical patch sensor 106 includes a short-range wireless transmitter84, and the processing component 18 features an embedded, matchedshort-range wireless transceiver 89. The optical patch sensor 106attaches free from wires to the patient's forehead 70 to increasemobility and flexibility. The short-range wireless transceiver 89 ispreferably a transmitter operating on a wireless protocol, e.g.Bluetooth™, 802.15.4 or 802.11. A preferred processing component 18 is apersonal digital assistant (PDA) or cellular phone that operates withthe above-described ABPM with little or no modifications. For example,the processing component 18 can be a PDA that includes a wireless CDMAchipset, such as the MSM family of mobile processors manufactured byQualcomm, each of which includes an internal Bluetooth™ radio. Suitablechipset within this family include the MSM6025, MSM6050, and theMSM6500, and are described and compared in detail inhttp://www.qualcomm.com. In addition to circuit-switched voice calls,the wireless transmitters used in these chipsets transmit data in theform of packets at speeds up to 307 kbps in mobile environments.

The processing component 18 preferably supports a custom firmwareapplication that displays and analyzes information for the ABPM 20. Thefirmware application is typically written to operate on a variety ofmobile device operating systems including BREW, Palm OS, Java, PocketPC, Windows CE, and Symbian. A more detailed explanation of the customfirmware application is disclosed in co-pending U.S. patent applicationSer. No. 10/967511, filed on Oct. 18, 2004, for a CUFFLESSBLOOD-PRESSURE MONITOR AND ACCOMPANYING WIRELESS MOBILE DEVICE, thecontents of which have been previously incorporated by reference.

FIG. 3 shows a system 120 wherein a physician calibrates theabove-described ABPM 20 for a particular patient 70 and additionallyenters blood pressure limits used in the conditioned response alertsystem. In a preferred embodiment, the physician initiates thecalibration process using a personal computer 15 that sends a signalthrough a wired connection 34 to a processing component 19 within theABPM 20. In response, the processing component 19 measures and processesoptical and electrical waveforms collected by the optical patch sensor105 to determine the patient's calibration parameters. These calibrationparameters are described in more detail in BLOOD PRESSURE MONITORINGDEVICE FEATURING A CALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610;filed Oct. 18, 2004) and PATCH SENSOR FOR MEASURING BLOOD PRESSUREWITHOUT A CUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005), thecontents of which have been previously incorporated herein by reference.The system 120 correlates the calibration parameters to blood pressureby subsequently measuring the patient's blood pressure using acalibration device 100, typically a conventional blood-pressure cuff,which temporarily attaches to an upper portion 112 of the patient's arm.Immediately after measuring the calibration parameters, the personalcomputer 15 sends a second signal through a second wired connection 95to a controller 110 embedded within the calibration device 100. Thesignal directs the controller 110 to initiate the cuff-based bloodpressure measurement using a motor-controlled pump 102. Once the signalis received, the calibration device 100 collects blood pressure values(e.g. systolic and diastolic pressures), and sends these back throughthe wired connection 95 to the personal computer 15. The system 120repeats this process at a later time (e.g., 15 minutes later) to collecta second set of calibration parameters. The physician then removes thecalibration device 100. The personal computer 15 then calculates acalibration table associating the calibration parameters and bloodpressure values that passes through the wired connection 34 to theprocessing component 19 within the ABPM, where it is stored in memory.The ABPM uses the calibration table for all future cuffless measurementsof blood pressure.

Once the ABPM 20 is calibrated, the physician enters blood pressurelimits into the personal computer 15. The blood pressure limits passthrough the wired connection 34 to the processing component 19, wherethey are stored in memory. During an actual measurement, the processingmodule 19 compares the patient's blood pressure measured with the ABPM20 to the blood pressure limits stored in memory to determine if thepatient's blood pressure is trending high or low. If this is the case,the controller 19 initiates an audio and/or visual alert as describedabove.

FIG. 4 shows a preferred embodiment of an Internet-based system 53 thatoperates in concert with the ABPM 20 to send information from a patientthrough a wireless network 54 to a web site 66 hosted on anInternet-based host computer system 57. A secondary computer system 69accesses the website 66 through the Internet 67. The system 53 functionsin a bi-directional manner, i.e. the ABPM 20 can both send and receivedata. Most data flows from the ABPM 20; using the same network, however,the monitor 20 can also receive data (e.g., calibration parameters,pre-determined blood pressure levels, software upgrades, and textmessages indicating ‘alerts’ or trending blood pressure) through thewireless network 54. A wireless gateway 55 connects to the wirelessnetwork 54 and receives data from one or more ABPMs. The wirelessgateway 55 additionally connects to a host computer system 57 thatincludes a database 63 and a data-processing component 68 for,respectively, storing and analyzing the data. The host computer system57, for example, may include multiple computers, software pieces, andother signal-processing and switching equipment, such as routers anddigital signal processors. The wireless gateway 55 preferably connectsto the wireless network 54 using a TCP/IP-based connection, or with adedicated, digital leased line (e.g., a frame-relay circuit or a digitalline running an X.25 or other protocols). The host computer system 57also hosts the web site 66 using conventional computer hardware (e.g.computer servers for both a database and the web site) and software(e.g., web server and database software).

During typical operation, the patient continuously wears the ABPM 20 fora period of time, ranging from a 1-2 days to weeks. For longer-termmonitoring (e.g. several months), the patient may wear the ABPM 20 forshorter periods of time during the day. To view information sent fromthe ABPM 20, the patient or medical professional accesses a userinterface hosted on the web site 66 through the Internet 67 from thesecondary computer system 69. The system 53 may also include a callcenter, typically staffed with medical professionals such as doctors,nurses, or nurse practioners, whom access a care-provider interfacehosted on the same website 66.

In an alternate embodiment, the host computer system 57 includes a webservices interface 70 that sends information using an XML-based webservices link to a secondary, web-based computer application 71. Thisapplication 71, for example, could be a data-management system operatingat a hospital.

FIGS. 5A and 5B show an adhesive patch sensor 205 according to theinvention that features a pair of LEDs 210, 212 and photodetector 214that, when attached to a patient, generate an optical waveform (231 inFIG. 6). A horseshoe-shaped metal electrode 217 surrounds these opticalcomponents and generates an electrical waveform (232 in FIG. 6). Theelectrical and optical waveforms, once generated, pass through a cable218 to a processing module, which analyzes them as described in detailbelow to measure a patient's systolic and diastolic blood pressure,heart rate, and pulse oximetry. The patch sensor 205 features anadhesive component 219 that adheres to the patient's skin and securesthe LEDs 210, 212, photodetector 214, and electrode 217 in place tominimize the effects of motion.

During operation, the cable 218 snaps into a plastic header 216 disposedon a top portion of the patch sensor 205. Both the cable 218 and header216 include matched electrical leads that supply power and ground to theLEDs 210, 212, photodetector 214, and electrode 219. The cable 218 andheader 216 additionally supply a high-frequency electrical signal to theelectrode that helps generate the electrical waveform. When the patchsensor 205 is not measuring optical and electrical waveforms (e.g., whenthe patient is sleeping), the cable 218 unsnaps from the header 216,while the sensor 205 remains adhered to the patient's skin. In this waya single sensor can be used for several days. After use, the patientremoves and then discards the sensor 205.

To measure blood pressure, heart rate, and pulse oximetry, the LEDs 210,212 generate, respectively, red and infrared radiation that irradiatesan underlying artery. Blood volume increases and then decreases as theheart pumps blood through the patient's artery. Blood cells within theblood absorb and transmit varying amounts of the red and infraredradiation depending the on the blood volume and how much oxygen binds tothe cells' hemoglobin. The photodetector 214 detects a portion of theradiation that reflects off an underlying artery, and in response sendsa radiation-induced photocurrent to an analog-to-digital converterembedded within the processing component. The analog-to-digitalconverter digitizes the photocurrent to generate a time-dependentoptical waveform for each wavelength. In addition, the microprocessoranalyzes waveforms generated at both red and infrared wavelengths, andcompares a ratio of the relative absorption to a calibration table codedin its firmware to determine pulse oximetry. The microprocessoradditionally analyzes the time-dependent properties of one of theoptical waveforms to determine the patient's heart rate.

Concurrent with measurement of the optical waveform, the electrode 219detects an electrical impulse from the patient's skin that theprocessing component processes to generate an electrical waveform. Theelectrical impulse is generated each time the patient's heart beats.

The patch sensor 205 preferably has a diameter, ‘D’, ranging from 0.5centimeter (‘cm’) to 10 cm, more preferably from 1.5 cm to 3.0 cm, andmost preferably 2.5 cm. The patch sensor 205 preferably has a thickness,‘T’, ranging from 1.0 millimeter (“mm”) to 3 mm, more preferably from1.0 mm to 1.5 mm, and most preferably 1.25 mm. The patch sensor 205preferably includes a body composed of a polymeric material such as aneoprene rubber. The body is preferably colored to match a patient'sskin color, and is preferably opaque to reduce the affects of ambientlight. The body is preferably circular in shape, but can also benon-circular, e.g. an oval, square, rectangular, triangular or othershape.

FIG. 6 shows both optical 231 and electrical 232 waveforms generated bythe patch sensor of FIGS. 5A and 5B and used in the calibrationprocedure described above. Following a heartbeat, the electrical impulsetravels essentially instantaneously from the patient's heart to thepatch sensor, where the electrode detects it to generate the electricalwaveform 232. At a later time, a pressure wave induced by the sameheartbeat propagates through the patient's arteries and arrives at thesensor, where the LEDs and photodetector detect it as described above togenerate the optical waveform 231. The propagation time of theelectrical impulse is independent of blood pressure, whereas thepropagation time of the pressure wave depends strongly on pressure, aswell as mechanical properties of the patient's arteries (e.g., arterialsize, stiffness). The microprocessor runs an algorithm that analyzes thetime difference ΔT between the arrivals of these signals, i.e. therelative occurrence of the optical 231 and electrical 232 waveforms asmeasured by the patch sensor.

In still other embodiments, the above-described system can receiveinputs from other measurement devices, such as weight scales,glucometers, EKG/ECG monitors, cuff-based blood pressure monitors,dietary monitors, pedometers and other exercise monitors, and GPSsystems.

Still other embodiments are within the scope of the following claims.

1. A system for monitoring blood pressure, the system comprising: amonitoring device comprising a patch sensor component that generates anoptical signal; and a processing component configured to process theoptical signal with calibration information to obtain blood pressureinformation, and then compare the blood pressure information to apre-programmed value to generate a signal.
 2. The system of claim 1,further comprising an audio component.
 3. The system of claim 2, whereinthe audio component is further configured to receive the signal and inresponse generate an audio alert.
 4. The system of claim 1, furthercomprising a display component.
 5. The system of claim 4, wherein thedisplay component is further configured to receive the signal and inresponse display an alert message.
 6. The system of claim 1, furthercomprising a drug-delivery system.
 7. The system of claim 1, furthercomprising a wireless transceiver.
 8. The system of claim 7, wherein thewireless transceiver is further configured to send and receiveinformation through a wireless network.
 9. The system of claim 8,further comprising an Internet-based system configured to sendinformation through the wireless network to the wireless transceiver,and receive information through the wireless network from the wirelesstransceiver.
 10. The system of claim 8, wherein the Internet-basedsystem is further configured to send information describing a bloodpressure level to the processing component.
 11. A method for monitoringa patient, comprising the following steps: outfitting the patient with aambulatory blood pressure monitor comprising an optical system thatmeasures blood pressure without using a cuff, and a wireless systemconfigured to send and receive information sent from an Internet-basedsystem through a wireless network; sending from the Internet-basedsystem to the ambulatory blood pressure monitor a signal that indicatesa blood pressure level; comparing a blood pressure value measured withthe ambulatory blood pressure monitor to the blood pressure level; andgenerating a signal in response to the comparing step.
 12. The method ofclaim 11, further comprising a step for generating an audio alert inresponse to the signal.
 13. The method of claim 12, wherein the audioalert indicates to the patient that their blood pressure value is aboveor below the blood pressure level.
 14. The method of claim 12, furthercomprising a step for generating a visual alert in response to thesignal.
 15. The method of claim 14, wherein the visual alert indicatesto the patient that their blood pressure value is above or below theblood pressure level.